LTC1174HVCN8-3.3#TR [Linear]
IC 1 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PDIP8, 0.300 INCH, PLASTIC, DIP-8, Switching Regulator or Controller;
| 型号： | LTC1174HVCN8-3.3#TR |
| 厂家： | 
Linear |
| 描述： | IC 1 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PDIP8, 0.300 INCH, PLASTIC, DIP-8, Switching Regulator or Controller 转换器 |
| 文件： | 总16页 (文件大小：354K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1174
LTC1174-3.3/LTC1174-5
High Efficiency
Step-Down and Inverting
DC/DC Converter
U
DESCRIPTIO
EATURE
S
F
The LTC®1174 is a simple current mode DC/DC converter
ideally suited for 9V to 5V, 5V to 3.3V, or 5V to –5V
operation. With an internal 0.9Ω switch (at a supply
voltage of 9V), the LTC1174 requires only four external
components to construct a complete high efficiency
DC/DC converter.
■
High Efficiency: Up to 94%
Peak Inductor Current Independent of
Inductor Value
■
■
■
■
■
■
■
■
■
■
■
Short-Circuit Protection
Optimized for 5V to –5V Applications
Wide VIN Range: 4V to 18.5V
Low Dropout Operation
Under a no load condition the LT1174 draws only 130µA.
In shutdown, it draws a mere 1µA making this converter
ideal for current sensitive applications. In dropout, the
internal P-channel MOSFET switch is turned on continu-
ously allowing the user to maximize the life of the battery
source.
Low-Battery Detector
Pin Selectable Current Limit
Internal 0.9Ω Power Switch: VIN = 9V
Only Four External Components Required
130µA Standby Current
Active Low Micropower Shutdown
The maximum inductor current of the LTC1174 family is
pin selectable to either 340mA or 600mA, optimizing
efficiency for a wide range of applications. Operation up to
200kHz permits the use of small surface mount inductors
and capacitors.
O U
PPLICATI
S
A
■
■
■
■
■
■
Distributed Power Systems
Step-Down Converters
Inverting Converters
Memory Backup Supply
Portable Instruments
Battery-Powered Equipment
For applications requiring higher output current or ultra-
high efficiency, see the LTC1148 data sheet.
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
U
O
TYPICAL APPLICATI
High Efficiency Step-Down Converter
LTC1174-5 Efficiency
V
IN
9V
100
3 ×
15µF*
25V
+
6
V
95
IN
3
2
8
1
5
V
IN
= 6V
LB
LB
SHUTDOWN
IN
90
85
80
75
70
V
OUT
OUT
SW
V
= 9V
IN
5V
175mA
7
I
PGM
100µH†
LTC1174-5
+
100µF**
10V
1N5818
GND
4
1174 TA01
L = 100µH
V
PGM
= 5V
= 0V
OUT
(3) AVX TPSD156K025
AVX TPSD107K010
*
**
I
† COILTRONICS CTX100-4
1
10
LOAD CURRENT (mA)
100 200
1174 TA02
1
LTC1174
LTC1174-3.3/LTC1174-5
W W W
U
ABSOLUTE AXI U RATI GS
(Voltage Referred to GND Pin)
Operating Temperature Range .................... 0°C to 70°C
Extended Commercial
Temperature Range ................................ –40°C to 85°C
Junction Temperature (Note 1)............................ 125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Input Supply Voltage (Pin 6)
LTC1174 ................................................ –0.3V to 13.5V
LTC1174HV ............................................–0.3V to 18.5V
Switch Current (Pin 5) ............................................... 1A
Switch Voltage (Pin 5)
LTC1174 ..................................................... VIN – 13.5V
LTC1174HV ................................................ VIN – 18.5V
W
U
/O
PACKAGE RDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
TOP VIEW
TOP VIEW
LTC1174CN8
LTC1174CS8
LTC1174CN8-3.3
LTC1174CS8-3.3
V
(V *)
OUT FB
1
2
3
4
8
7
6
5
SHUTDOWN
V (V *)
OUT FB
1
2
3
4
SHUTDOWN
8
7
6
5
LTC1174CN8-5
LTC1174HVCN8
LTC1174HVCN8-3.3
LTC1174HVCN8-5
LTC1174IN8
LTC1174CS8-5
LTC1174IS8
LTC1174HVCS8
LTC1174HVCS8-3.3
LTC1174HVCS8-5
LB
I
LB
I
OUT
PGM
OUT
PGM
LB
V
IN
LB
IN
V
IN
IN
GND
SW
GND
SW
S8 PACKAGE
8-LEAD PLASTIC SOIC
N8 PACKAGE
8-LEAD PLASTIC DIP
* ADJUSTABLE OUTPUT VERSION
* ADJUSTABLE OUTPUT VERSION
S8 PART MARKING
1174
1174HV
1174H3
1174H5
TJMAX = 125°C, θJA = 110°C/W
TJMAX = 125°C, θJA = 150°C/W
117433
117450
1174I
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
TA = 25°C, VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
1
UNITS
µA
I
V
V
Feedback Current
Feedback Voltage
LTC1174/LTC1174HV
LTC1174/LTC1174HV
FB
●
1.20
1.25
1.30
V
V
V
FB
Regulated Output Voltage
LTC1174-3.3/LTC1174HV-3.3
LTC1174-5/LTC1174HV-5
●
●
3.14
4.75
3.30
5.00
3.46
5.25
OUT
∆V
Output Voltage Line Regulation
Output Voltage Load Regulation
V
= 6V to 12V, I
= 100mA, I
= V (Note 2)
10
70
mV
OUT
IN
LOAD
PGM
IN
LTC1174-3.3 (Note 2)
20mA < I
20mA < I
< 175mA, I
< 400mA, I
= 0V
–5
–45
–70
–70
mV
mV
LOAD
LOAD
PGM
PGM
= V
IN
LTC1174-5 (Note 2)
20mA < I
20mA < I
< 175mA, I
< 400mA, I
= 0V
–5
–50
–70
–70
mV
mV
LOAD
LOAD
PGM
PGM
= V
IN
2
LTC1174
LTC1174-3.3/LTC1174-5
TA = 25°C, VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Input DC Supply Current (Note 3)
Active Mode
LTC1174: 4V < V < 12V, I
LTC1174HV: 4V < V < 16V, I
Q
= 0V
PGM
450
450
600
600
µA
µA
IN
= 0V
IN
PGM
Sleep Mode
LTC1174: 4V < V < 12V
LTC1174HV: 4V < V < 16V
130
130
180
180
µA
µA
IN
IN
SHUTDOWN (Note 4)
LTC1174: V
= 0V, 4V < V < 12V
1
2
10
25
µA
µA
SHUTDOWN
IN
LTC1174HV: V
= 0V, 4V < V < 16V
SHUTDOWN
IN
V
Low-Battery Trip Point
Current into Pin 3
Current Sunk by Pin 2
1.25
1.4
0.5
1.5
1.5
V
µA
mA
mA
LBTRIP
I
I
LBIN
LTC1174: V
LTC1174HV: V
= 0.4V
1.0
0.6
1.2
0.8
LBOUT
LBOUT
= 0.4V
LBOUT
V
Comparator Hysteresis
Current Limit
LTC1174/LTC1174HV
7.5
0.54
0.27
15
0.60
0.34
30
0.78
0.50
mV
A
A
HYST
I
I
= V , V
= 0V, V
= 0V
= 0V
●
●
PEAK
PGM
IN OUT
I
PGM
OUT
R
ON
ON Resistance of Switch
LTC1174
LTC1174HV
●
●
0.75
0.90
1.30
1.55
Ω
Ω
t
V
V
Switch Off-Time (Note 5)
SHUTDOWN Pin High
SHUTDOWN Pin Low
V
at Regulated Value
3
1.2
4
5
µs
V
V
OFF
OUT
Minimum Voltage at Pin 8 for Device to Be Active
Maximum Voltage at Pin 8 for Device to Be in Shutdown
IH
0.75
IL
I
SHUTDOWN Pin Input Current
LTC1174: V
LTC1174HV: V
= 12V
0.5
2.0
µA
IH
SHUTDOWN
= 16V
SHUTDOWN
I
SHUTDOWN Pin Input Current
0 ≤ V
≤ 0.8V
SHUTDOWN
0.5
µA
IL
–40°C ≤ TA ≤ 85°C (Note 6), for LTC1174I only.
SYMBOL PARAMETER
CONDITIONS
MIN
1.18
0.75
0.54
TYP
1.25
1.2
0.60
0.34
MAX
1.31
2
UNITS
V
V
FB
Feedback Voltage
Current Sunk by Pin 2
Current Limit
LTC1174I
I
I
V
= 0.4
mA
A
A
LBOUT
PEAK
LBOUT
I
I
= V , V
= 0V
= 0V
0.78
PGM
PGM
IN OUT
= 0V, V
OUT
t
Switch Off-Time (Note 5)
V
OUT
at Regulated Value
2
4
6
µs
OFF
The
● denotes specifications which apply over the full operating
Note 2: Guaranteed by design.
Note 3: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 4: Current into pin 6 only, measured without electrolytic input
temperature range.
Note 1: T is calculated from the ambient temperature T and power
dissipation P according to the following formulas:
J
A
D
LTC1174CN8, LTC1174CN8-3.3, LTC1174CN8-5:
capacitor.
T = T + (P ×110°C/W)
J
A
D
Note 5: The off-time is wafer-sort trimmed.
LTC1174CS8, LTC1174CS8-3.3, LTC1174CS8-5:
T = T + (P ×150°C/W)
Note 6: The LTC1174I is not tested and not quality assurance sampled at
–40°C and 85°C. These specifications are guaranteed by design and/or
correlation.
J
A
D
3
LTC1174
LTC1174-3.3/LTC1174-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Load Current
Efficiency vs Load Current
Efficiency vs Load Current
100
95
90
85
80
75
70
100
95
90
85
80
75
70
100
95
90
85
80
75
70
V
IN
= 6V
V
V
IN
= 6V
V
IN
= 6V
= 9V
V
IN
= 9V
IN
V
IN
= 9V
L = 50µH
L = 100µH
L = 50µH
V
PGM
COIL = CTX50-4
= 5V
= 0V
OUT
V
I
= 5V
V
I
= 5V
OUT
PGM
OUT
PGM
I
= V
= V
IN
IN
COIL = CTX100-4
COIL = CTX50-4
1
10
LOAD CURRENT (mA)
100 200
1
10
100
500
1
10
100 400
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1174 G01
1174 G03
1174 G02
Efficiency vs Load Current
Efficiency vs Load Current
Efficiency vs Load Current
100
90
80
70
60
50
100
90
80
70
60
50
100
90
80
70
60
50
V
IN
= 5V
V
IN
= 5V
V
V
IN
= 5V
V
= 9V
= 9V
V
IN
= 9V
IN
IN
L = 50µH
L = 50µH
L = 100µH
V
PGM
COIL = CTX50-4
= 3.3V
V
PGM
COIL = CTX50-4
= 3.3V
V
= 3.3V
OUT
OUT
OUT
I
= 0V
I
= V
I
= V
IN
PGM IN
COIL = CTX100-4
1
10
100
300
1
10
100
500
1
10
100 500
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1174 G04
1174 G05
1174 G06
Switch Leakage Current
vs Temperature
Line Regulation
Efficiency vs Input Voltage
6
4
180
160
140
120
100
80
95
94
93
92
91
90
89
88
87
V
= 13.5V
I = 100mA
LOAD
I = 0V
PGM
IN
2
0
L = 100µH
L = 50µH
–2
–4
–6
–8
–10
–12
–14
60
V
I
I
= 5V
OUT
PGM
LOAD
40
= 0V
= 75mA
20
CORE = CTX (Kool Mµ®)
0
0
4
6
8
10
12
14
0
20
40
60
80
100
2
9
5
7
10 11 12 13 14
6
8
INPUT VOLTAGE (V)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
1174 G07
1174 G08
1174 G09
Kool Mµ® is a registered trademark of Magnetics, Inc.
4
LTC1174
LTC1174-3.3/LTC1174-5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
DC Supply Current
Supply Current in Shutdown
Efficiency vs Input Voltage
500
95
94
93
92
91
90
89
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
I
= 0V
PGM
ACTIVE MODE
V
= 5V
OUT
SHUTDOWN = 0V
450
400
350
300
250
200
150
100
50
L = 100µH
T
= 25°C
A
I
= V
IN
PGM
COIL = CTX100-4
CURRENT INTO PIN 6 ONLY
I
I
= 100mA
LOAD
= 0V
PGM
I
= 300mA
LOAD
I
= V
PGM
IN
SLEEP MODE
T
A
= 25°C
2
0
0
4
6
8
10
12
14
5
6
7
8
9
10 11 12 13 14
0
4
6
8
10
12
14
2
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1174 G12
1174 G10
1174 G11
Operating Frequency
vs VIN – VOUT
Switch Resistance vs
Input Voltage
Off-Time vs Output Voltage
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
50
40
30
20
10
0
2.0
1.5
1.0
0.5
0
T
A
= 25°C
V
= 5V
OUT
T
= 25°C
A
T
= 70°C
A
LTC1174HV
LTC1174
LTC1174-5
LTC1174HV-5
LTC1174-3.3
LTC1174HV-3.3
0
1
2
3
4
5
4
6
8
10 12 14 16 18 20
INPUT VOLTAGE (V)
1174 G14
3
5
6
7
8
9
0
2
1
4
OUTPUT VOLTAGE (V)
(V – V ) VOLTAGE (V)
IN
OUT
1174 G15
1174 G13
U
U
U
PI FU CTIO S
SW(Pin5):DrainoftheP-ChannelMOSFETSwitch.Cathode
VOUT (VFB)(Pin1):FortheLTC1174,thispinconnectstothe
main voltage comparator’s input. On the LTC1174-3.3 and
LTC1174-5 this pin goes to an internal resistive divider
which sets the output voltage.
of Schottky diode must be closely connected to this pin.
VIN (Pin 6): Input Supply Voltage. It must be decoupled
close to ground pin 4.
LBOUT (Pin 2): Open Drain of an N-Channel Pull-Down. This
pin will sink current when pin 3 (LBIN) goes below 1.25V.
During shutdown this pin goes to high impedance.
IPGM (Pin 7): Selects the Current Limit of the P-Channel
Switch. With IPGM = VIN, the current trip point is 600mA and
with IPGM = 0V, the current trip value is reduced to 340mA.
LBIN (Pin 3): The “–” Input of the Low-Battery Voltage
Comparator. The “+” input is connected to a reference
voltage of 1.25V.
SHUTDOWN (Pin 8): Pulling this pin to ground keeps the
internal switch off and puts the LTC1174 in micropower
shutdown.
GND (Pin 4): Ground Pin.
5
LTC1174
LTC1174-3.3/LTC1174-5
U
U
W
FU CTIO AL DIAGRA
(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)
V
IN
6
V
V
LIM2
LIM1
+
I
PGM
7
R
SENSE
A5
SLEEP
V
0.1Ω
TH2
+
–
–
A2
–
+
A4
RESET
SET
Q
C
g
V
FB
T
m
V
(V )
OUT FB
V
TH1
1
5
×
SW
LB
IN
R1*
LB
2
4
3
OUT
V
FB
–
+
–
+
A1
31.5k
A3
SHUTDOWN
1.25V
REFERENCE
8
GND
1174 BD
* R1 = 51k FOR LTC1174-3.3
R1 = 93.5k FOR LTC1174-5
U
(Refer to Functional Diagram)
OPERATIO
The LTC1174 uses a constant off-time architecture to
switch its internal P-channel power MOSFET. The off-time
is set by an internal timing capacitor and the operating
frequency is a function of VIN.
The timing capacitor, CT, begins to discharge until its
voltage goes below VTH1. Comparator A4 will then trip,
which resets the flip-flop and causes the switch to turn on
again. Also, the timing capacitor is recharged. The inductor
current will again ramp up until the current comparator A2
trips. The cycle then repeats.
The output voltage is set by an internal resistive divider
(LTC1174-3.3 and LTC1174-5) or an external divider re-
turned to VFB pin 1 (LTC1174). A voltage comparator A1
compares the divided output voltage to a reference voltage
of 1.25V.
When the load is relatively light, the LTC1174 automatically
goes into Burst Mode operation. The current mode loop is
interrupted when the output voltage reaches the desired
regulated value. The hysteretic voltage comparator A1 trips
when VOUT is above the desired output voltage, shutting off
the switch and causing the timing capacitor to discharge.
This capacitor discharges past VTH1 until its voltage drops
below VTH2. Comparator A5 then trips and a sleep signal is
generated.
Tooptimizeefficiency, theLTC1174automaticallyswitches
between continuous and Burst ModeTM operation. The volt-
age comparator is the primary control element when the
device is in Burst Mode operation, while the current com-
parator controls the output voltage in continuous mode.
During the switch“ON” time, switch current flows through
the 0.1Ω sense resistor. When this current reaches the
thresholdofthecurrentcomparatorA2,itsoutputsignalwill
change state, setting the flip-flop and turning the switch off.
In sleep mode, the LTC1174 is in standby and the load
current is supplied by the output capacitor. All unused
Burst ModeTM is a trademark of Linear Technology Corporation.
6
LTC1174
LTC1174-3.3/LTC1174-5
U
(Refer to Functional Diagram)
OPERATIO
circuitry is shut off, reducing quiescent current from
wheretOFF =4µsandVD isthevoltagedropacrossthediode.
0.45mAto0.13mA.Whentheoutputcapacitordischarges Note that the operating frequency is a function of the input
by the amount of the hysteresis of the comparator A1, the and ouput voltage.
P-channel switch turns on again and the process repeats
itself.
Although the size of the inductor does not affect the fre-
quency, it does affect the ripple current. The peak-to-peak
ripple current is given by:
Operating Frequency and Inductor
Since the LTC1174 utilizes a constant off-time architecture,
itsoperatingfrequencyisdependentonthevalueofVIN.The
frequency of operation can be expressed as:
V
OUT + VD
I
RIPPLE = 4 ×10−6
A
P−P
(
)
L
By choosing a smaller inductor, a low ESR output filter
capacitorhastobeused(seeCIN andCOUT).Moreover,core
losswill also increase(seeInductor CoreSelection section)
due to higher ripple current.
V − VOUT
1
tOFF
IN
f =
Hz
( )
V + V
IN
D
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PPLICATI
I FOR ATIO
A
100
Inductor Core Selection
CTX100-4
90
With the value of L selected, the type of inductor must be
chosen. Basically there are two kinds of losses in an
inductor, core and copper
CTX100-4P
80
Core losses are dependent on the peak-to-peak ripple
current and the core material. However it is independent of
the physical size of the core. By increasing the inductance
the inductor’s peak-to-peak ripple current will decrease,
therefore reducing core loss. Utilizing low core loss mate-
rial, such as molypermalloy or Kool Mµwill allow users to
concentrate on reducing copper loss and preventing satu-
ration.Figure1showstheeffectofdifferentcorematerialon
the efficiency of the LTC1174. The CTX core is Kool Mµand
the CTXP core is powdered iron (material 52).
70
V
V
PGM
= 5V
60
50
IN
= 3.3V
IN
OUT
I
= V
1
10
100
500
LOAD CURRENT (mA)
100
90
80
70
60
50
CTX50-4
CTX50-4P
Although higher inductance reduces core loss, it increases
copperlossasitrequiresmorewindings.Whenspaceisnot
a premium larger gauge wire can be used to reduce the wire
resistance. This also prevents excessive heat dissipation.
V
= 5V
IN
OUT
V
= 3.3V
CIN
I
= V
PGM
IN
In continuous mode the source current of the P-channel
MOSFETisasquarewaveofdutycycleVOUT/VIN.Toprevent
large voltage transients, a low ESR input capacitor sized for
1
10
100
500
LOAD CURRENT (mA)
1174 F01
Figure 1. Efficiency Using Different Types of
Inductor Core Material
7
LTC1174
LTC1174-3.3/LTC1174-5
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PPLICATI
A
S I FOR ATIO
the maximum RMS current must be used. The CIN RMS
current is given by:
the diode conducts only a small fraction of the time. The
most stressful condition for the diode is when the output is
short-circuited. Under this condition the diode must safely
handle IPEAK at close to 100% duty cycle. A fast switching
diode must also be used to optimize efficiency. Schottky
diodes are a good choice for low forward drop and fast
switching times. Most LTC1174 circuits will be well served
by either a 1N5818, a MBRS140T3 or a MBR0520L Schot-
tky diode.
1/2
IOUT VOUT V − V
(
)
IN
OUT
[
]
IRMS
≈
A
RMS
(
)
V
IN
This formula has a maximum at VIN = 2VOUT, where IRMS
=
IOUT/2.Thissimpleworstcaseiscommonlyusedfordesign
becauseevensignificantdeviationsdonotoffermuchrelief.
Note that ripple current directly affects capacitor’s lifetime.
DONOTUNDERSPECIFYTHISCOMPONENT.Anadditional
0.1µF ceramic capacitor is also required on VIN for high
frequency decoupling.
Short-Circuit Protection
The LTC1174 is protected from output short by its internal
current limit. Depending on the condition of IPGM pin, the
limit is either set to 340mA or 600mA. In addition, the off-
time of the switch is increased to allow the inductor’s
current to decay far enough to prevent any current build-up
(see Figure 2).
COUT
To avoid overheating, the output capacitor must be sized to
handle the ripple current generated by the inductor. The
worst case RMS ripple current in the output capacitor is
given by:
IPGM = VIN
I
PEAK
2
I
≈
A
RMS
(
)
RMS
= 170mA or 300mA
IPGM = 0
Although the output voltage ripple is determined by the
hysteresis of the voltage comparator, ESR of the output
capacitor is also a concern. Too high of an ESR will create
ahigherrippleoutputvoltageandatthesametimecausethe
LTC1174 to sleep less often. This will affect the efficiency of
the LTC1174. For a given technology, ESR is a direct
function of the volume of the capacitor. Several small-sized
capacitors can also be paralleled to obtain the same ESR as
one large can. Manufacturers such as Nichicon, Chemicon
and Sprague should be considered for high performance
capacitors. The OS-CON semiconductor dielectric capaci-
tor available from Sanyo has the lowest ESR for its size, at
a higher price.
GND
1174 F02
L = 100µH
IN = 13.5V
20µs/DIV
V
Figure 2. Inductor's Current with Output Shorted
Low-Battery Detector
Thelow-batteryindicatorsensestheinputvoltagethrough
anexternalresistivedivider. Thisdividedvoltageconnects
to the “–” input of a voltage comparator (pin 3) which is
comparedwitha1.25Vreferencevoltage. Withthecurrent
going into pin 3 being negligible, the following expression
is used for setting the trip limit:
Catch Diode Selection
Thecatchdiodecarriesloadcurrentduringtheoff-time.The
average diode current is therefore dependent on the
P-channel switch duty cycle. At high input voltages the
diode conducts most of the time. As VIN approaches VOUT
R4
R3
V
= 1.25 1+
LBTRIP
8
LTC1174
LTC1174-3.3/LTC1174-5
O U
S
W
U
PPLICATI
I FOR ATIO
A
INPUT VOLTAGE
V
IN
4V TO 12V
LTC1174
R4
3
+
+
+
6
–
+
2 × 47µF*
0.1µF
V
16V
IN
3
2
7
8
1
5
R3
LB
LB
SHUTDOWN
IN
1.25V
V
OUT
OUT
REFERENCE
1174 F03
I
SW
PGM
50µH**
LTC1174HV-5
GND
2 × 47µF*
16V
V
MBRS140T3
Figure 3. Low-Battery Comparator
4
OUT
–5V
LTC1174 Adjustable Applications
45mA
AVX TPSD476K016
COILTRONICS CTX50-4
*
**
1174 F05
The LTC1174 develops a 1.25V reference voltage between
thefeedback(pin1)terminalandground(seeFigure4).By
selecting resistor R1, a constant current is caused to flow
through R1 and R2 to set the overall output voltage. The
regulated output voltage is determined by:
Figure 5. Positive-to-Negative 5V Converter
Figure 5, giving the circuit a 1.5V of headroom for VIN.
Note that the circuit can operate from a minimum of 4V,
making it ideal for a 4 NiCad cell application. For a higher
output current circuit, please refer to the Typical Applica-
tions section.
2
R
V
= 1.25 1 +
OUT
R1
Board Layout Checklist
For most applications, a 30k resistor is suggested for R1.
To prevent stray pickup, a 100pF capacitor is suggested
across R1 located close to the LTC1174.
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1174. These items are also illustrated graphically in
the layout diagram in Figure 6. Check the following in your
layout:
V
OUT
R2
R1
1
LTC1174
V
FB
1. Is the Schottky catch diode closely connected between
ground (pin 4) and switch (pin 5)?
100pF
2. Is the “+” plate of CIN closely connected to VIN (pin 6)?
This capacitor provides the AC current to the internal
P-channel MOSFET.
1174 F04
Figure 4. LTC1174 Adjustable Configuration
3. Is the 0.1µF VIN decoupling capacitor closely conected
between VIN (pin 6) and ground (pin 4)? This capacitor
carries the high frequency peak currents.
Inverting Applications
The LTC1174 can easily be set up for a negative output
voltage. If –5V is desired, the LTC1174-5 is ideal for this
application as it requires the least components. Figure 5
shows the schematic for this application. Note that the
output voltage is now taken off the GND pin. Therefore,
the maximum input voltage is now determined by the
differencebetweentheabsolutemaximumvoltagerating
and the output voltage. A maximum of 12V is specified in
4. Is the SHUTDOWN (pin 8) actively pulled to VIN during
normal operation? The SHUTDOWN pin is high imped-
ance and must not be allowed to float.
5. Is the IPGM (pin 7) pulled either to VIN or ground? The
IPGM pin is high impedance and must not be allowed
to float.
9
LTC1174
LTC1174-3.3/LTC1174-5
O U
W
U
PPLICATI
A
S I FOR ATIO
8
7
6
1
V
OUT
FB
SHUTDOWN
(V
)
2
3
LB
I
OUT
OUTPUT DIVIDER
PGM
REQUIRED WITH
ADJUSTABLE
R1
R2
V
V
LB
V
IN
IN
IN
LTC1174
0.1µF
VERSION ONLY
C
IN
4
5
SW
GND
D
L
BOLD LINES INDICATE
HIGH CURRENT PATH
C
OUT
+
OUT
1174 F06
Figure 6. LTC1174 Layout Diagram (See Board Layout Checklist)
DESIGN EXAMPLE
As a design example, assume VIN = 9V (nominal), VOUT
=
(example:CoiltronicsCTX50-4). Theoperatingfrequency,
neglecting voltage across diode VD is:
5V, and IOUT = 350mA maximum. The LTC1174-5 is used
forthisapplication,withIPGM (pin7)connectedtoVIN.The
minmum value of L is determined by assuming the
LTC1174-5 is operating in continuous mode.
V
V
5
OUT
f ≈ 2.5 ×10 1−
IN
= 111kHz
I
PEAK
With the value of L determined, the requirements for CIN
and COUT are calculated. For CIN, its RMS current rating
should be at least:
= I
AVG CURRENT
OUT
I
+ I
V
PEAK
2
=
I
V
= 350mA
1/ 2
]
I
V
V − V
(
)
OUT
[
OUT IN OUT
I
=
A
RMS
TIME
(
)
1174 F07
RMS
V
IN
Figure 7. Continuous Inductor Current
= 174mA
For COUT, the RMS current rating should be at least:
With IOUT = 350mA and IPEAK = 0.6A (IPGM = VIN), IV =
0.1A.The peak-to-peak ripple inductor current, IRIPPLE, is
0.5A and is also equal to:
IPEAK
IRMS
≈
A
RMS
(
)
2
= 300mA
V
OUT + VD
I
RIPPLE = 4 ×10−6
A
P−P
(
)
NowallowVIN todropto6V.Atthisminimuminputvoltage
the operating frequency will decrease. The new frequency
is 42kHz.
L
Solving for L in the above equation and with VD = 0.6V,
L = 44.8µH. The next higher standard value of L is 50µH
10
LTC1174
LTC1174-3.3/LTC1174-5
O U
W
U
PPLICATI
S I FOR ATIO
A
Table 1. Inductor Manufacturers
Table 2. Capacitor Manufacturers
MANUFACTURER
PART NUMBER
MANUFACTURER
PART NUMBER
AVX Corporation
P.O. Box 887
Myrtle Beach, SC 29578
(803) 448-9411
TPS Series
TAJ Series
Coilcraft
DT3316 Series
1102 Silver Lake Road
Cary, IL 60013
(708) 639-2361
Coiltronics Inc.
Econo-Pac
Octa-Pac
Nichicon America Corporation
927 East State Parkway
Schaberg, IL 60173
PL Series
6000 Park of Commerce Blvd.
Boca Raton, FL 33487
(407) 241-7876
(708) 843-7500
Sanyo Video Components
2001 Sanyo Avenue
San Diego, CA 92173
(619) 661-6385
OS-CON Series
Gowanda Electronics Corporation
1 Industrial Place
Gowanda, NY 14070
GA10 Series
(716) 532-2234
Sumida Electric Co. Ltd.
637 E. Golf Road, Suite 209
Arlington Heights, IL 60005
(708) 956-0666/7
CD 54 Series
CD 75 Series
Attn: Sales Dept.
U
O
TYPICAL APPLICATI S
6V to 5V Step-Down Regulator with Low-Battery Detection
INPUT VOLTAGE
6V
2 ×
47µF**
16V
+
+
6
0.1µF
4.7k
LOW-BATTERY INDICATOR
*
V
IN
IS SET TO TRIP AT V = 5.5V
IN
*LOW-
BATTERY
8
1
5
7
2
3
I
SHUTDOWN
PGM
AVX TPSD476K016
= MBRS140T3 (SURFACE MOUNT)
1N5818
**
D1
INDICATOR
LB
V
OUT
OUT
162k
† L1 SELECTION
LTC1174-5
V
OUT
MANUFACTURER PART NO. TYPE
SW
5V
LB
IN
L1†
100µH
COILTRONICS
SUMIDA
GOWANDA
CTX100-4 SURFACE MOUNT
CD75-101 SURFACE MOUNT
GA10-103K THROUGH HOLE
365mA
2 ×
GND
4
47.5k
D1
47µF**
16V
1174 TA03
High Efficiency 3.3V Regulator
INPUT VOLTAGE
4V TO 12.5V
3 ×
+
6
22µF*
0.1µF
V
IN
25V
8
1
7
3
I
SHUTDOWN
PGM
LB
LB
V
IN
OUT
50µH†
LTC1174-3.3
V
OUT
2
5
SW
3.3V
OUT
425mA
+
2 ×
GND
4
AVX TPSD226K025
*
1N5818
47µF**
AVX TPSD476K016
**
16V
† COILTRONICS CTX50-4
1174 TA04
11
LTC1174
LTC1174-3.3/LTC1174-5
U
O
TYPICAL APPLICATI S
High Efficiency 3V Regulator
INPUT VOLTAGE
4V TO 12.5V
3 ×
+
6
22µF*
0.1µF
V
IN
25V
8
1
5
7
3
I
SHUTDOWN
PGM
100pF
LB
LB
V
IN
FB
50µH†
V
LTC1174
OUT
2
3V
SW
OUT
450mA
42k
30k
GND
4
+
2 ×
100µF**
1N5818
10V
AVX TPSD226K025
AVX TPSD105K010
*
1174 TA05
**
† COILTRONICS CTX50-4
Positive-to-Negative (–5V) Converter
INPUT VOLTAGE
4V TO 12.5V
*LOW-BATTERY INDICATOR
V
(V) I
4
6
8
10
(mA)
IN
OUT MAX
110
IS SET TO TRIP AT V = 4.4V
IN
2 ×
10µF**
35V
+
+
6
**AVX TPSD106K035
***AVX TPSD105K010
D1= MBRS130LT3 (SURFACE MOUNT)
1N5818
0.1µF
4.7K
140
V
IN
170
*LOW-
BATTERY
8
1
5
7
2
3
I
SHUTDOWN
PGM
200
† L1 SELECTION
12.5
235
INDICATOR
LB
LB
V
OUT
OUT
280k
LTC1174HV-5
MANUFACTURER
PART NO.
TYPE
SW
IN
COILTRONICS
COILCRAFT
SUMIDA
CTX50-3
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
L1†
50µH
DT3316-473
CD54-470
GA10-472K
GND
4
100µF***
10V
43k
D1
GOWANDA
V
OUT
–5V
1174 TA06
Positive-to-Negative (– 3.3V) Converter
INPUT VOLTAGE
4V TO 13.5V
* LOW-BATTERY INDICATOR
2 ×
+
IS SET TO TRIP AT V = 4.4V
6
IN
V
(V) I
4
5
6
7
(mA)
IN
OUT MAX
175
33µF**
0.1µF
4.7K
** AVX TPSD336K020
*** AVX TPSD105K010
D1 = MBRS140T3 (SURFACE MOUNT)
1N5818
V
IN
20V
*LOW-
BATTERY
8
1
5
7
2
3
205
I
SHUTDOWN
PGM
230
255
INDICATOR
† L1 SELECTION
LB
LB
V
OUT
OUT
220k
LTC1174HV-3.3
SW
MANUFACTURER
PART NO.
TYPE
IN
COILTRONICS
COILCRAFT
SUMIDA
CTX50-3
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
L1†
50µH
2 ×
100µF***
10V
+
DT3316-473
CD54-470
GA10-472K
GND
4
43k
D1
V
OUT
GOWANDA
–3.3V
210mA
1174 TA07
12
LTC1174
LTC1174-3.3/LTC1174-5
U
O
TYPICAL APPLICATI S
Negative Boost Converter
AVX TPSD336K020
= MBRS140T3 (SURFACE MOUNT)
1N5818
*
6
D1
V
IN
310k
† L1 SELECTION
8
1
5
7
I
SHUTDOWN
PGM
MANUFACTURER
PART NO.
TYPE
2 ×
+
2
3
0.1µF
33µF*
COILTRONICS
COILCRAFT
SUMIDA
CTX50-3
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
LB
V
OUT
OUT
20V
DT3316-473
CD54-470
GA10-472K
LTC1174-3.3
SW
LB
IN
GOWANDA
2 ×
33µF*
16V
+
0.1µF
50k
L1†
50µH
GND
4
D1
V
OUT
–9V
175mA
INPUT VOLTAGE
–5V
1174 TA08
9V to 5V Pre-Post Regulator
INPUT
VOLTAGE
6V TO 12.5V
+
100µF*
16V
6
0.1µF
V
IN
3
2
7
8
1
5
SANYO OS-CON
*
**
D1
LB
SHUTDOWN
IN
AVX TPSD476K016
100pF
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
LB
I
V
FB
OUT
†
V
LTC1174
OUT
8
5
1
V
OUT
LT1121-5
5V
SW
IN
PGM
L1†
MANUFACTURER PART NO.
TYPE
SURFACE MOUNT
DT3316-473 SURFACE MOUNT
CD54-470 SURFACE MOUNT
GA10-472K THROUGH HOLE
150mA
110k††
30.1k††
GND
4
COILTRONICS
COILCRAFT
SUMIDA
CTX50-3
50µH
2 ×
47µF**
16V
+
+
1µF
SOLID
TANTALUM
SHUTDOWN
0.1µF
D1
GND
3
GOWANDA
†† USE 1% METAL FILM RESISTORS
1174 TA09
LCD Display Power Supply
INPUT
VOLTAGE
4V TO 12.5V
V
(V)
I
4
(mA)
IN
OUT MAX
20
5
6
25
56.2k††
6
30
7
35
V
IN
8
43
3
8
1
5
LB
SHUTDOWN
IN
2N2222
2N5210
9
50
10
11
12
55
7
2
50k††
60
I
PGM
V
FB
65
LTC1174
LB
SW
OUT
AVX TAJE106K050
AVX TPSD476K016
= MBRS140T3 (SURFACE MOUNT)
1N5818
*
1N914
GND
4
998k††
**
Si9035
D1
D1
0.1µF
V
OUT
† L1 SELECTION
–24V
2 ×
47µF**
16V
+
50mA AT
V
MANUFACTURER PART NO.
TYPE
SURFACE MOUNT
DT3316-104 SURFACE MOUNT
CD75-101 SURFACE MOUNT
GA10-103K THROUGH HOLE
0.1µF
= 9V
4 ×
IN
L1†
100µH
COILTRONICS
COILCRAFT
SUMIDA
CTX100-3
10µF*
+
50V
GOWANDA
1174 TA10
††
USE 1% METAL FILM RESISTORS
13
LTC1174
LTC1174-3.3/LTC1174-5
U
O
TYPICAL APPLICATI S
9V to 5V, –5V Outputs
INPUT VOLTAGE
4V TO 12.5V
SANYO OS-CON
WIMA MKS2
*
+
+
+
+
**
6
100µF*
† COILTRONICS CTX100-4
0.1µF
0.1µF
20V
V
IN
V
(V)
I
(mA)
8
7
IN
OUT MAX
75
I
SHUTDOWN
PGM
4
6
100
1
5
3
2
LB
LB
V
8
IN
OUT
SW
125
V
3.3µF**
OUT
10
12
13
145
LTC1174-5
5V
160
OUT
L1A†
100µH
135mA AT
180
V
IN
= 9V
GND
4
L1B†
100µH
100µF*
16V
3
2
MBRS140T3
MBRS140T3
CTX100-4
L1A
L1B
1
4
+
100µF*
16V
–V
OUT
–5V
135mA AT
IN
V
= 9V
1174 TA11
9V to 12V, –12V Outputs
INPUT VOLTAGE
4V TO 12.5V
* AVX TAJD226K035
** WIMA MKS2
3 ×
+
6
3
2
† COILTRONICS CTX100-4
0.1µF
22µF*
V
†† USE 1% METAL FILM RESISTORS
IN
SHUTDOWN
CTX100-4
L1A
35V
L1B
8
1
5
7
I
1
4
PGM
V
IN
(V)
I
4
(mA)
OUT MAX
20
3
2
LB
LB
V
IN
FB
3.3µF**
5
6
25
V
OUT
LTC1174
Si9430DY
35
12V
SW
OUT
L1A†
100µH
7
45
55mA AT
IN
2
+
1
50
301k††
34k††
4
3
8
V
= 9V
GND
4
2 ×
22µF*
35V
L1B†
100µH
9
55
1N914
10
11
12
62
MBRS140T3
67
73
+
2 × 22µF*
–V
OUT
MBRS140T3
35V
–12V
55mA AT
1174 TA12
V
IN
= 9V
14
LTC1174
LTC1174-3.3/LTC1174-5
U
O
TYPICAL APPLICATI S
Automatic Current Selection
INPUT
VOLTAGE
6V TO 12.5V
6
100k
V
IN
8
1
5
2
7
3
LB
I
SHUTDOWN
TPO610L
OUT
+
100µF*
V
0.1µF
PGM
OUT
20V
V
50µH†
OUT
LTC1174-5
5V
LB
SW
IN
0mA TO
320mA
GND
4
100k
100k
+
100µF*
1N5818
16V
36.5k
SANYO OS-CON CAPACITOR
*
1174 TA13
† COILTRONICS CTX50-4
Buck-Boost Converter
INPUT VOLTAGE
4V TO 12V
+
6
100µF*
20V
0.1µF
V
IN
8
1
5
7
I
SHUTDOWN
PGM
* SANYO OS-CON
** WIMA MKS2
3
2
† COILTRONICS CTX100-4
IN
OUT
LB
LB
V
3.3µF**
V
LTC1174HV-5
OUT
5V
160mA
SW
OUT
L1A†
2
1
4
3
GND
4
100µH
3
2
L2A†
100µH
+
CTX100-4
L1A
100µF*
16V
L1B
1N5818
1
4
1174 TA14
Battery Charger
INPUT VOLTAGE
8V TO 12.5V
V
IN
(V)
I
8
9
10
11
12
(mA)
OUT MAX
320
+
* AVX TAJD226K020
** AVX TAJD107K010
D1,D2 = MBRS140T3
(SURFACE MOUNT)
1N5818
6
2 × 22µF*
0.1µF
20V
325
V
IN
8
1
5
330
7
I
SHUTDOWN
PGM
335
335
† L1 SELECTION
3
2
LB
LB
V
FB
IN
D2
MANUFACTURER
PART NO.
CTX50-2P
TYPE
LTC1174
V
OUT
TO
SW
COILTRONICS
COILCRAFT
SUMIDA
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
OUT
4 NiCAD BATTERY
L1†
50µH
DT3316-473
CD54-470
GA10-472K
150k
GND
4
+
100µF**
10V
GOWANDA
D1
33k
1174 TA15
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LTC1174
LTC1174-3.3/LTC1174-5
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
N8 Package
8-Lead Plastic DIP
0.400*
(10.160)
MAX
8
7
6
5
4
0.255 ± 0.015*
(6.477 ± 0.381)
1
2
3
0.130 ± 0.005
0.300 – 0.325
0.045 – 0.065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
0.125
0.015
(0.380)
MIN
(3.175)
MIN
+0.025
0.045 ± 0.015
(1.143 ± 0.381)
0.325
–0.015
+0.635
8.255
(
)
–0.381
0.100 ± 0.010
(2.540 ± 0.254)
0.018 ± 0.003
(0.457 ± 0.076)
N8 0694
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm).
S8 Package
8-Lead Plastic SOIC
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157*
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
SO8 0294
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
LT/GP 0894 2K REV B • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
16
●
●
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
LINEAR TECHNOLOGY CORPORATION 1994
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